An arrest warrant alleges an empty flask that smelled of alcohol was found in the vehicle of a Dallas firefighter arrested after a crash that killed a pregnant woman and her unborn child.

A witness told police he saw Horace Shaw's vehicle pass him on U.S. Highway 67 at a speed between 100 to 110 mph before it collided with 18-year-old Alyssa Pimental's vehicle early in the morning on Dec. 13. in Cedar Hill.

The unnamed witness said he stopped to help and saw Shaw exit his vehicle and approach Pimental, who had been ejected from her vehicle, the warrant states. The witness told police Shaw identified himself as a paramedic before he laid on the ground near Pimental.

Alyssa Pimentel (Facebook)

Another witness told police she too observed Shaw's vehicle traveling at a high speed shortly before the crash. She also stopped to help and told officers Shaw couldn't walk straight.

According to the affidavit, Shaw wouldn't speak with officers at the scene and later asked for an attorney when questioned at the hospital.

Police say the passenger in Shaw's vehicle told officers they were at Thibodeaux's in Dallas before the crash. According to the affidavit, the passenger admitted Shaw was "speeding a little bit" as they traveled southbound on the highway. The passenger didn't answer when asked if the pair had been drinking, the warrant states.

Pimental was several months pregnant at the time of the crash and the baby didn't survive. Her boyfriend, a passenger in the car, suffered serious injuries but survived. Both Shaw and his passenger were treated for non-life-threatening injuries.

Shaw was charged with intoxication manslaughter with a vehicle, which is a second-degree felony.