Today in Pictures: July 12

Bonfires burn in Belfast, trains collide in Italy, a somber memorial in Dallas and more of Tuesday's best pictures.

Five seats are left empty in honor of the five slain police officers during a memorial service in Dallas on July 12. The officers were ambushed at a protest last week. Tom Pennington / Getty Images
Former president George W. Bush, first lady Michelle Obama and President Barack Obama hold hands during a memorial service for the five slain police officers in Dallas on July 12. President Obama paid tribute to the officers, saying their deaths should remind Americans of their common ideals. CARLO ALLEGRI / Reuters
The balloon of Russian adventurer Fedor Konyukhov rises as he embarks on his attempt to break the world record for a solo hot-air balloon flight around the globe near Perth, Australia, on July 12. Oscar Konyukhov / Reuters
A boy displaced in recent fighting plays on a volleyball net at an Anglican church compound in Juba, South Sudan, on July 12. An uneasy calm settled over South Sudan's capital on Tuesday after the country's leader and his top rival both demanded a cease-fire. Renewed fighting between opposing army forces has raised fears of a return to civil war in the East African country, which marked its fifth anniversary of independence over the weekend while panicked residents hid inside their homes. Reuters

Two smashed carriages are thrown across the tracks after a head-on collision between two trains between Ruvo and Corato, in the southern Italian region of Puglia, on July 12. At least 25 people died and dozens were injured on Tuesday when two passenger trains collided head-on at high speed in southern Italy, sending debris flying into surrounding olive groves. 

PHOTOS: Italian Trains Collide

Vigili del Fuoco via AFP - Getty Images
A bonfire still smolders in front of three houses that burned as a result of the start of annual Twelfth of July celebrations held by Loyalists in the Shankill Road area in Belfast, Northern Ireland. The Orange marches and demonstrations celebrate the Battle of the Boyne in 1690 when the Protestant King William of Orange defeated the Catholic King James II on the banks of the river Boyne. CLODAGH KILCOYNE / Reuters
Sen. Bernie Standers stands with Democratic presidential candidate Hillary Clinton after he endorsed her at a campaign rally in Portsmouth, New Hampshire, on July 12. Sanders' endorsement capped a contentious presidential primary race and solidified the former secretary of state's hold on the Democratic Party. BRIAN SNYDER / Reuters
Revelers run around the cow in the bull ring during the Cow's Festival at the end of the sixth running of the bulls at the San Fermin Festival in Pamplona, northern Spain, on July 12. Revelers from around the world flock to Pamplona every year to take part in the eight-day festival made famous by Ernest Hemingway's 1920 novel "The Sun Also Rises." Alvaro Barrientos / AP
South Korean police detain a member of a part-time employment union during a rally against the government's labor policy in Seoul on July 12. The protesters demanded an increase in the hourly minimum wage to 10,000 South Korean Won (around $8.71). JUNG BYUNG-HYUK / EPA

Britain's Home Secretary Theresa May, the next prime minister of the United Kingdom, gestures to the media after attending a cabinet meeting at 10 Downing Street in London on July 12. May will become the new prime minister on Wednesday evening after David Cameron visits the Queen to officially resign his position.

Monday in Pictures: Portugal's Heroes Return and More

Kirsty Wigglesworth / AP