Dallas - Nearly a week after five officers were killed by a gunman in Dallas, memorial services for three of them drew thousands of mourners on Wednesday.Services were held for Dallas Area Rapid Transit (DART) officer Brent Thompson, Dallas police Sergeant Michael Smith and Dallas police Senior Corporal Lorne Ahrens - all three slain in downtown Dallas on Thursday by a sniper during a march to protest recent fatal shootings of black men in Minnesota and Louisiana by police. The two other services are scheduled for Friday and Saturday.The service for Thompson, 43, drew hundreds of law enforcement officers in crisp formal uniforms to The Potter's House, the Dallas megachurch headed by celebrity Bishop TD Jakes.Thompson's wife Emily, a fellow DART officer whom he had recently married, called the shooter, Micah Johnson, a coward. "You know your hate made us stronger," she told the audience.Johnson was killed when authorities used a robot to detonate an explosive as negotiations faltered. Nine officers and two civilians were injured in the attack.A funeral service for Thompson was scheduled for later on Wednesday in Corsicana, south of Dallas. He is the first DART officer killed in the line of duty since the agency's police force was founded in 1989.Also on Wednesday, a few hundred mourners gathered for a Catholic funeral service in the suburb of Farmers Branch for Smith, a former US Army Ranger known for his upbeat attitude and compassionate approach to others.Smith joined the Dallas police force in 1989. He once received a "Cops' Cop" award from the Dallas Police Association.A public service was scheduled on Thursday for Smith at a Dallas church where he worked security.In the Dallas suburb of Plano, mourners were told of Ahrens' work with the Los Angeles County sheriff's department and time as semi-pro football player before moving to Texas and joining the Dallas police force. Ahrens was known as a gentle giant and a voracious reader whose intelligence was equal to his size.Dallas police officer Michael Krol's funeral is set for Friday, and Dallas police officer Patrick Zamarripa's funeral will be held on Saturday.