Surveillance video from a Los Angeles 7-Eleven store shows the man suspected of fatally stabbing UCLA grad student Brianna Kupfer buying a vape pen and chatting with a clerk just 30 minutes after the heinous attack, police say.

The LAPD is asking for the public’s help identifying the suspect accused of killing the 24-year-old at her job at a luxury furniture store on North Le Brea Avenue.

The suspected killer of 24-year-old UCLA grad student Brianna Kupfer appeared on surveillance video at a nearby 7-Eleven store buying a vape pen just 30 minutes after her murder.

The suspected killer of 24-year-old UCLA grad student Brianna Kupfer appeared on surveillance video at a nearby 7-Eleven store buying a vape pen just 30 minutes after her murder. (LAPD)

Video shows him wearing sunglasses and a dust mask, buying a vape with cash inside a 7-Eleven store at Beverly and Wilshire boulevards, police said in a Tuesday news briefing.

For a moment, he pulls down his mask to say something to the clerk, whose face is blurred in the version of the video police released Tuesday. Then he grabs some coins from the take-a-penny tray on the counter and hands them over along with a bill.

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The suspected killer of 24-year-old UCLA grad student Brianna Kupfer appeared on surveillance video at a nearby 7-Eleven store buying a vape pen just 30 minutes after her murder.

Suspect in Brianna Kupfer stabbing seen on 7-Eleven surveillance video less than an hour after her murder. (LAPD)

After paying, he turns back from the door and places the vape down on the counter, and the clerk takes it and appears to hand him another, the video shows. Then he leaves for good.

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At around 1:30 p.m. PT on Jan. 13, the man allegedly entered Croft House and apparently didn't go unnoticed by Kupfer.  Police revealed Tuesday she texted a friend minutes before her death that there was a man inside the store creeping her out.

"She sent a text to a friend letting her know that there was someone inside the location that was giving her a bad vibe," LAPD Lt. John Radtke said of the Jan. 13 slaying. "Regrettably, that person did not see the text immediately."

The suspect is described as a thin Black man who is more than 6 feet tall. He has short dreadlocks. In surveillance video after the attack, he is wearing a black, long-sleeved shirt, dark gray chinos and a dark blue backpack. 

Police warned that anyone who sees him should call 911 and not approach.

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Anyone with information should call Los Angeles police at 213-382-9470.

Fox News’ Rebecca Rosenberg contributed to this report.