By Jon Herskovitz and Lisa Maria Garza

DALLAS (Reuters) – Thousands of police officers joined by ordinary citizens attended funerals on Wednesday for three of the policemen shot dead in a racially motivated ambush attack last week that intensified America’s long-running debate on race and justice.

At the Dallas megachurch called The Potter’s House, officers by the thousands crowded into the funeral for Dallas Area Rapid Transit officer Brent Thompson, who had married a fellow officer just two weeks before last Thursday’s attack.

“I know many of you have dealt with these things quite often,” pastor Rick Lamb of Northside Baptist Church told the crowd. “Today is about Brent and trying to bring some closure to this family as they finish the job that they didn’t want to start, but had to start last week.”

Funerals were also taking place on Wednesday for Sergeant Michael Smith, 55, and Officer Lorne Ahrens, 48, of the Dallas Police Department.

The funerals came a day after President Barack Obama praised the slain officers’ heroism, condemned the attack as an “act not just of demented violence but of racial hatred” and made an impassioned plea for national unity.

The five officers were killed by a former U.S. Army Reserve soldier who told police that he was angry about police killings of two black men in Louisiana and Minnesota earlier that week and wanted to “kill white people,” especially police.

Funerals for the other two slain officers, Michael Krol, 40, and Patrick Zamarripa, 32, are expected later in the week.

The shootings in Louisiana and Minnesota were the latest in a series of high-profile police killings of black men in various U.S. cities that have brought intense scrutiny of police use of force, particularly against black suspects.

The police slain in Dallas last week were patrolling a demonstration decrying the killings by police of Alton Sterling, 37, in Baton Rouge, Louisiana, and Philando Castile, 32, outside St. Paul, Minnesota. Sterling was killed after officers responded to a call that he had threatened someone with a gun. Castile was killed during a traffic stop.

In Baton Rouge, Sterling’s 15-year-old son, Cameron Sterling, urged people to refrain from violence as they demand reforms in the U.S. criminal justice system.

“I feel that people in general, no matter what the race is, should come together as one united family,” Cameron Sterling told reporters in the parking lot of the Triple S Food Mart, where his father was killed. “I want everyone to protest the right way. Protest in peace. … No violence, whatsoever.”

Justin Bamberg, a lawyer for Sterling’s son, said he hoped the officer who shot Sterling would be criminally charged following the federal investigation into the incident.

“We want justice. We want an indictment,” Bamberg said.

A lawyer for the officer has denied race was a factor in Sterling’s shooting.

Protests against police violence continued on Wednesday. In Minneapolis, a mixed-race group of several dozen protesters briefly closed the southbound lanes of a major highway, linking arms and chanting “Black Lives Matter.”

(Additional reporting by Letitia Stein in Baton Rouge, Louisiana, Colleen Jenkins in Winston-Salem, North Carolina, and Justin Madden in Chicago; Writing by Scott Malone; Editing by Will Dunham)