HOUSTON -- An 18-year-old Lamar High School student has died after a shooting happened near the school Tuesday afternoon. A 15-year-old female student was grazed by a bullet, Houston Police reported.

HPD homicide detectives believe the male victim was targeted by three suspects who got away.

Related: Police find car used in deadly shooting near Lamar High School; suspect search continues

The gunman, who was wearing a mask, walked up and shot the victim a second time while he was lying on the ground, according to witnesses.

The suspects got away in a black car.

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An 18-year-old Lamar High School student has died after a shooting near the school. A 15-year-old female student was grazed by a bullet. (Air 11)

"Very disappointing that it's come to this point in our city. I've said it before, we're not just going to stand by. We need the public's support. Somebody knows these individuals who were in that vehicle.

"Somebody has seen this car, especially with the plastic bag on the back window." said Asst. Chief Finner during a press conference with the media Tuesday afternoon.

Houston Police Chief Art Acevedo tweeted they believe this was a gang-related shooting.

Mayor Sylvester Turner also provided a statement on the shooting, saying, in part, "The city of Houston will not tolerate gang activity or any senseless violence on our streets, especially not the kind that targets young people. Our children are off limits. I want parents and students to feel protected and confident while they are near or inside a school."

Raw video: Officials provide details on fatal shooting of Lamar High School students

Police have not released descriptions of the suspects and they are asking for anyone with any information to come forward.

"Stand up and say something. I've said this before, today it's somebody else's kid. Tomorrow it can be yours. Or your sister, your brother." Finner pleaded.

The assistant chief also had a message for the suspects.

"We're not just going to stand by and let our streets become blood baths. We're not," Finner said. "And people say, 'Well, you know, you said that a couple of months ago,' and you know what? I will fight for the safety of our citizens. It's most important, and all of our resources and all of our partnerships will go to removing these violent criminals."

A construction worker captured the sound of shots on a Facebook live video Tuesday afternoon.

The shooting did not happen at Lamar High, but the school was placed on lockdown as a precaution.

The shooting happened around 12:15 p.m. Tuesday in the 2800 block of Bammel Lane near West Alabama.

Nearby St. John's School was also placed on lockout after it happened.

Finner said patrols would be beefed up in the area. He offered advice for students shaken by the shooting.

"I would tell the students let's get through this together. Always be aware of your surroundings but don't change your way of life, keep living life and let's work together as the city of Houston always does come together for whatever we're going through. Keep living your life and let's hang in here together and get this information to us and we can get these dangerous individuals." Finner said.

Lamar students and staff are still mourning the murder-suicide deaths of two 15-year-old students on Nov. 8. That shooting happened at an apartment complex on Buffalo Speedway.

HISD Superintendent Grenita Latham said counselors are available to students and faculty on campus if they need.