PEOPLE Explains: Christmas Eve Crash That Killed Expectant Mom, Baby Soon After She Got Engaged

An expectant young mother and her infant son were killed on Christmas Eve in a fiery crash that police believe was caused by a drunk driver — who now faces homicide charges.

The victim’s fiancé survived and has spoken out about the family he lost.

Here are four things to know about what happened.

1. Crash Was Caused by Driver Allegedly Fleeing Another Crash: Police

Jillian Pamela Ramsay, 36, was involved in a crash about 8:44 p.m. on Sunday when she fled that scene and continued north on LA Highway 1065 “at a high rate of speed,” Louisiana State Police alleged in a news release obtained by PEOPLE.

As she continued driving, she came up behind a car driven by Ryan Joseph McCollum Sr., 24, who was accompanied by his fiancée, 19-year-old Shelly Mulkey, and their 7-month-old son, Ryan McCollum Jr., police said.

Ramsay allegedly swerved, hitting the back of McCollum’s vehicle and rupturing the gas can — igniting both cars.

Ramsay received only minor injuries in the crash and left her vehicle on her own, according to police. But witnesses had to remove both McCollum and Mulkey, performing CPR on Mulkey, while their little boy was left inside their car “quickly became engulfed in flames.”

Mulkey and Ryan Jr. were pronounced dead at the scene.

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2. Drinking and Speed Led to the Crash, Authorities Say

State police said blood tests were done on both Ramsay and McCollum and that “troopers determined Jillian Ramsay was impaired at the time of the crash.” She was treated at an area hospital and released, after which she was charged with two counts of vehicular homicide as well as hit-and-run and careless operation, police said.

She was booked into Louisiana’s Tangipahoa Parish Jail, and records there show she remains in custody as of Thursday morning. It is unclear if she has entered a plea or retained an attorney who could comment on her behalf.

The crash investigation continues and seat-belt use for all four people involved is “unknown,” police said.

“Tragically, two completely preventable factors led to this horrific crash. The on-scene supervisor and crash scene investigators determined alcohol impairment and speed were the primary elements that led to this crash,” state police said in the news release. “The poor decisions/criminal actions of one person has led to devastating consequences for everyone involved.

“There is no task more difficult than the one faced by Troopers in making death notification on Christmas Eve. That difficulty was magnified with the loss of a child. Troopers implore Louisiana motorists to make safe decisions behind the wheel.”

3. Slain Fiancée Had Just Gotten Engaged

After surviving the crash that killed Mulkey and their son, McCollum told The Advocate he proposed to Mulkey earlier that Sunday, as a Christmas Eve present — and she said yes. That same weekend, he said, they’d learned that Mulkey was pregnant with their second child.

McCollum told the newspaper his leg was injured in the crash and his face and ears were burned. He said the trio was returning from a family Christmas party and had just stopped at a gas station before the wreck.

Of Mulkey, his girlfriend of about four years, he said, “She was an awesome mama and an awesome friend I just want to hold them both in my arms again so bad.”

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4. ‘That’s Three Lives She Took From Me,’ Dad Says

Mulkey’s father, Billy Mulkey, also spoke out to The Advocate, sharing how McCollum had asked him for permission to propose to Shelly, which he gave.

“Whatever makes my babies happy,” Billy said.

He said he saw Shelly earlier that Sunday, before the crash, and had given her a gag gift of a Daisy BB gun. Reportedly a native of Tangipahoa Parish, Shelly worked at Hoppin Harley’s Interstate Travel Center before staying at home as a mom.

She was smart and giving, her father said. Her son, Ryan, was “the best baby you ever seen in the world.”

“I don’t care if he had a fever of 101. If you look at him and smile, he’s going to start smiling and laughing and jumping around,” he said.

While Billy told the paper he has sympathy for Ramsay — “That woman is going to have to live with that the rest of her life.” — he believes she should be prosecuted: “That’s three lives she took from me.”