A moment of silence in honor of the victims of the Boston Marathon bombing is observed on Boylston Street near the race finish line, exactly one week after the tragedy, on April 22, in Boston, Mass.

A woman wipes a tear at a memorial for the victims of the Boston Marathon bombing on Boylston Street near the race finish line, on April 22, in Boston, Mass. At 2:50 p.m., exactly one week after the bombings, many bowed their heads and cried at the makeshift memorial on Boylston Street, three blocks from the site of the explosions, where bouquets of flowers, handwritten messages, and used running shoes were piled on the sidewalk.

Officials line Boylston Street near the site of the explosions as they observe a moment of silence for the victims of the Boston Marathon bombings in Boston, Mass., on April 22.

Traders on the floor at the New York Stock Exchange join the moment of silence in honor of the Boston Marathon victims, on April 22.

Lt. Mike Murphy of the Newton, Mass., fire dept., carries an American flag down the middle of Boylston Street after observing a moment of silence in honor of the victims of the Boston Marathon bombings, on April 22, in Boston, Mass.

Muslim Brotherhood supporters throw stones towards opponents during clashes on April 19, in central Cairo.

Egyptian protesters clash near a bus belonging to Muslim Brotherhood supporters burns after it was reportedly set alight by anti- government protesters in Cairo, Egypt, Friday, April 19.

Muslim Brotherhood members hit an anti-government protester during clashes near Cairo's Tahrir Square, April 19.

The family of Kaufman County District Attorney Mike McLelland and his wife, Cynthia, comfort each other during their funeral services at the First Baptist Church of Wortham on April 5, in Wortham, Texas.

Pallbearers carry the remains of Kaufman County District Attorney Mike McLelland and his wife, Cynthia, out of the First Baptist Church of Wortham after their funeral services on April 5, in Wortham, Texas.

Texas Gov. Rick Perry looks on as a flag is folded to present to the family of Kaufman County District Attorney Mike McLelland and his wife, Cynthia after a memorial services in Mesquite, Texas on April 4.

An anti-Morsi protester stands with the national flag after protesters burned Muslim Brotherhood buses during clashes near the Muslim Brotherhood's national headquarters in Cairo's Moqattam district on March 22, 2013.

Muslim Brotherhood supporters conduct Friday noon prayers in front of the main headquarters of the Brotherhood in Cairo on March 22, 2013.

Egyptians shout anti-Muslim Brotherhood slogans during a march from downtown to the main Brotherhood headquarters in the hilltop neighborhood of Muqattam, Cairo, Egypt, on March 22, 2013. Thousands of protesters from different areas of Cairo are marching on Friday to express their rejection of the Muslim Brotherhood and President Mohammed Morsi's rule.

Supporters of the Egyptian Muslim Brotherhood clash with anti-government protesters near the movements' headquarters in Cairo on March 22, 2013.

Anti-Morsi protesters carry a Muslim Brotherhood member after hitting him during clashes near the Muslim Brotherhood's national headquarters in Cairo on March 22, 2013.

Egyptian policemen write a report at a destroyed branch headquarters of the Muslim Brotherhood after protesters broke in to the building in Cairo, Egypt, on March 22, 2013.

An Egyptian anti-Muslim Brotherhood protester throws a stone towards Muslim Brotherhood supporters during clashes near the party's national headquarters in Cairo on March 22.

An injured Egyptian anti-Muslim brotherhood protester is taken away by his comrades, during clashes near the Muslim Brotherhood's national headquarters in Cairo, Egypt, on March 22.

An Egyptian protester evacuates a wounded man during clashes between protesters and riot police near the state security building in Port Said, Egypt, on March 6.

An Egyptian man sets tiers ablaze during clashes in Port Said, Egypt, on March 6.

Egyptian army soldiers arrest an alleged rioter during clashes in Port Said, Egypt, on March 6.

Egyptians react from tear gas fired by riot police during clashes near the state security building in Port Said, Egypt, on March 6.

Anti-Morsi protesters are seen through a banner with pictures of people, who were killed in Port Said demonstrations since violence erupted after the court verdict on the sentencing of 21 people, at a camp in front of the Governorate General headquarters in Port Said city, 105 miles northeast of Cairo on March 5.

Free Syrian Army fighters and civilians react as they run after a jet missile hit the al-Myassar neighborhood of Aleppo, Syria, on Feb. 20.

People rescue a family member stuck in their house after a jet missile hit al-Myassar neighborhood of Aleppo, Syria, on Feb. 20.

Free Syrian Army fighters and civilians search for survivors under rubble after a jet missile hit the al-Myassar neighborhood of Aleppo, Syria, on Feb. 20.

A man carries a child who was wounded after a jet missile hit the al-Myassar neighborhood of Aleppo, Syria, on Feb. 20.

A Free Syrian Army fighter carries the remnant of a missile fired by a jet at the al-Myassar neighborhood of Aleppo, Syria, on Feb. 20.

Soldiers loyal to Syrian President Bashar al-Assad and their tank patrol the streets in al-Sabaa Bahrat district, an area controlled by Free Syrian Army fighters, in the center of Aleppo, Syria, on Feb. 20.

Syrians inspect destruction following an apparent surface-to-surface missile strike on the northern Syrian city of Aleppo on Feb. 19. The attack killed at least 20 people and another 25 were missing, opposition activists said on Tuesday. The missile was identified from its remains as a Scud-type rocket that government forces have increasingly used in areas under opposition control in the province of Aleppo and in the province of Deir a-Zor to the east, they said.

A member of the Free Syrian Army along with civilians search for survivors after a Syrian army rocket attack on the rebel-held Jabal Badro district in the city of Aleppo, on Feb. 19.

A member of the Free Syrian Army sits near where a Syrian army rocket attack took place at the rebel-held Jabal Badro district in the city of Aleppo, on Feb. 19.

Soldiers help mourners carry the coffin of slain opposition leader Chokri Belaid during his funeral procession towards the nearby cemetery of El-Jellaz, where he is to be buried, in the Jebel Jelloud district of Tunis, on Feb. 8. Tens of thousands of mourners chanted anti-Islamist slogans on Friday at the Tunis funeral of secular opposition leader Belaid, whose assassination has plunged Tunisia deeper into political crisis.

A couple mourns next to a Tunisian flag during the funeral procession for the late secular opposition leader Chokri Belaid in the Jebel Jelloud district in Tunis, on Feb. 8.

Thousands of Tunisians are gathered at el Jallez cemetery to attend the funerals of slain opposition leader Chokri Belaid, near Tunis, on Feb. 8. The Feb. 6 assassination of prominent government critic Chokri Belaid plunged the country into one of its deepest political crises since the overthrow of the dictatorship in 2011. The coffin is carried by pallbearers at center of picture.

Tunisians cover their faces as they stand at Jellaz cemetery amid teargas fired by police during the funeral of slain opposition politician Chokri Belaid, in Tunis, Tunisia, on Feb 8. Media reports state that Tunisian police fired tear gas outside the cemetery in the capital Tunis where thousands of people had gathered for the funeral of opposition leader Chokri Belaid. Belaid was shot dead by an unknown attacker outside his home on Feb. 6.

A protester flees from teargas fired by riot police during clashes with riot police near the cemetery where slain Tunisian opposition leader Chokri Belaid is buried on Feb. 8.

Protestors burn cars next to the cemetery where thousands of Tunisians are gathered to attend the funerals of slain opposition leader Chokri Belaid, near Tunis, on Feb. 8.

Thousands of Tunisians attend the funeral of slain opposition leader Chokri Belaid at el Jallez cemetery near Tunis, on Feb. 8. The Feb. 6 assassination of prominent government critic Chokri Belaid plunged the country into one of its deepest political crises since the overthrow of the dictatorship in 2011.

A tunisian woman wrapped in her national flag makes her way through tombs while attending the funeral of slain opposition leader Chokri Belaid at el Jallez cemetery near Tunis, on Feb. 8.

A hooded armed man stands guard in downtown Tecoanapa, in the southern Mexican state of Guerrero, on Jan. 24.

Hooded men stand guard outside the Justice palace, in Ayutla de los Libres, in the southern Mexican state of Guerrero, on Jan. 24.

Armed men guard the Justice palace from a car, in Ayutla de los Libres, in the southern Mexican state of Guerrero, on Jan. 24.

Some of the 27 people arrested by residents of Ayutla de los Libres, who have formed their own vigilante police force, are kept under custody inside a house in Ayutla de los Libres, on Jan. 25.

Angry crowds shout at suspected Islamist extremists in the back of an army truck in Gao, northern Mali, on Jan. 29. Four suspects were arrested after being found by a youth militia calling themselves the "Gao Patrolmen". Malian soldiers prevented the mob from lynching them.

Malian soldiers guard suspected Islamist extremists after throwing them in the back of the army truck in Gao, northern Mali, on Jan. 29.

Resident Ousmane Togo is reflected on a piece of broken mirror as he surveys the remains of a hotel hit by French air strikes in Douentza, Mali on Jan. 29. The hotel was used as a base for Islamists and was hit by French air strikes over a week ago.

A Malian tries to break the lock off a store front as looters and residents stand by in the streets of Timbuktu on Jan. 29. Hundreds of Malians looted stores in Timbuktu on Tuesday, saying the shops belonged to "Arabs" and "terrorists" linked to the radical Islamists who occupied the desert town for 10 months.

Looters crowd to get into a shop in the streets of Timbuktu on Jan. 29.

A Malian soldier tries to disperse looters in the streets of Timbuktu on Jan. 29.

Timbuktu residents plunder stores they say belong to Arabs, Mauritanians and Algerians who they accuse of supporting the Al Qaeda-linked Islamists during their 10-month rule over the ancient center of Islamic learning, on Jan. 29.