Follow CBSDFW.COM: Facebook | Twitter

DENTON (CBS11) – A U.S. Marine, 20-years-old and now behind bars for allegedly shooting and killing UNT student Sara Mutschlechner.

READ MORE: 2 Men Killed After Crane Falls On Pickup Truck On Texas Interstate

Denton Police believe Eric Jamal Johnson pulled the trigger on New Year’s Day and killed Mutschlechner after she was driving friends home from a party as the designated driver.

“I can tell you myself, I’ve driven by that intersection at least a half a dozen times so far and the first thing I think of is that’s the last moment Sara took her last breaths,” said Officer Shane Kizer with the Denton Police Department.

Police pointed out two main factors that they said helped lead to an arrest.

Investigators said Johnson had posted on Twitter about attending the party and had also posted pictures and descriptions of certain evidence that helped tie him to the case.

Investigators also were able to use “plate readers” to help confirm the vehicle that was allegedly used the moment of the shooting.

READ MORE: Woman Charged With Intoxication Manslaughter After Driving Pickup Head-On Into Victim's Car

Police said when they searched their database, they found a clear image of the vehicle to match their description.

No one answer the door at the family home where Johnson used to live

A friend who lives next door found it hard to piece together.

“He couldn’t have done this. That was my first reaction. I’m just shocked. Left me speechless you know,” said Arian Helm, a friend.

Investigators said they are still trying to figure out if anyone else will face charges.

Johnson is due back in court Thursday afternoon in Arizona where court officials said he will likely remain for 30 days. If he fights extradition, he could be there up to 90 days.

MORE NEWS: 2-Year-Old Dies After Ejected From Vehicle On Highway In Dallas

(©2016 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)