Police officers pay their respects ahead of the funeral for Officer Lorne Ahrens in Plano, Texas, US July 13, 2016. [Photo/Agencies]

DALLAS - 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."

As Thompson's funeral procession began the roughly 55-mile (89 km) journey back to his home of Corsicana, several police helicopters flew over the church as bagpipers played "Amazing Grace" and hundred of officers from different departments saluted his silver-colored casket.

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

Dallas police officer Eddie Coffey described Ahrens as a calming presence and a down-to-earth man.

"He was the guy you always wanted to show up as your backup," Coffey said. "He wanted to make sure everyone, from top down, made it home safely."