A Houston police officer was reportedly in stable condition Tuesday night after he was shot in the back during a traffic stop.

The Houston Chronicle reports Houston Police Department motorcycle officer Terry Smith, 47, was shot in the back at 6 p.m. in the Midtown area of the city. He is expected to remain in the hospital for a few more days to recover, the newspaper reports.

Police are still unsure who shot the 20-year police veteran and the motive behind it.

"It's unclear right now what the actual circumstances are. We really need the public's help on this one," said Victor Senties, an HPD spokesman.

Police do not think the traffic stop had anything to do with the shooting because the driver had already left Smith when the shot was fired.

Smith did not know what happened, Senties said. “All he knew was that he heard a loud 'pop' and felt some pain.”

A police captain had expressed concerns that biker groups could be targeting cops after the gang shooting in Waco, Fox 26 reports. The official told the station that a warning was sent out to police to watch out because they could be targeted.

Houston Fire Department paramedics arrived on the scene to examine Smith and found a gunshot wound in his back, officials said.

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