SAN ANTONIO – An officer who was shot at the downtown SAPD headquarters Sunday morning has died, police Chief William McManus said.

"This is everyone's worst nightmare," McManus told reporters.

Crime Stoppers is offering a $10,000 reward for information that leads to the identification and location of the gunman.

According to SAPD's website, Detective Benjamin Marconi was the 54th SAPD officer killed in the line of duty.

Police chief William McManus said Marconi, 50, a father of two from Floresville.

"Most families will be celebrating the holidays. SAPD will be burying one of its own because of an ultimate act of cowardice, but a suspect who will be caught and brought to justice," McManus said at a news conference.

Related: Officials react to officer slaying

McManus said right before noon, the officer was writing a ticket in his patrol car when a black Toyota or Nissan pulled up behind it. A man got out the vehicle and shot the officer twice, once in the head. Marconi was taken to San Antonio Military Medical Center, where he died, McManus said.

"I want to extend my deepest condolences to the family of the officer killed outside police headquarters today, as well as to our entire police force," Mayor Ivy Taylor said in a statement. "This type of crime cannot and will not be tolerated. I ask for the community's thoughtfulness and patience as the investigation continues and SAPD searches for the suspect."

Michael Helle, president of the San Antonio Police Officers Association, extended the union's condolences to the officer's family.

“Our prayers and love are with the family of our fallen officer. We will stand by the officer’s family and support them and their needs during this devastating time. The single worst event any police officer can face is the loss of a brother or sister in the line of duty. Words cannot express how deeply this affects every police officer, not just in San Antonio, but across our country. We are all hurting, but we are all a family and we will stand together, protect each other and protect our families."

The shooter was described as a black man around 5 feet 7 inches to 6 feet tall. He was wearing a gray shirt, black pants and appears to have a goatee.

Anyone with information is asked to call Crime Stoppers at 210-224-STOP (7867).

Jonathan Segura said that he witnessed the fatal shooting of a SAPD officer. He told reporters what he saw. (Note: The interview is in Spanish).

Posted by Ashly Custer Reporter on Sunday, November 20, 2016

The last SAPD officer fatally shot in the line of duty was Officer Bobby Deckard on Dec. 8, 2013. Deckard was shot in the head while pursuing two robbery suspects in a vehicle chase. He was in the intensive care unit for 13 days before he was pronounced dead. The two suspects, Shawn Ruiz Puente, 30 and Jenevieve Ramos, 28, were arrested and charged with capital murder.

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