MINNEAPOLIS (WCCO) — Some 15 months after a Wisconsin mother crashed into an oncoming truck, the district attorney says it’s a homicide case.

Kari Jo Milberg, 34, was driving. Her 11-year-old daughter and two of her 5-year-old nieces were killed.

The crash happened in Oak Grove Township in western Wisconsin back in December of 2013. Investigators say Milberg was exchanging Facebook messages less than 2 minutes before the crash.

The district attorney is charging Milberg with three counts of homicide by negligent operation and one count of reckless driving causing injury.

Milberg herself was thrown from the car and injured in the crash. For a time after the incident, she says she could not remember what happened.

Investigators now believe they’ve figured out what happened.

From the start, this crash rattled those around it — even the professionals. The day after the crash, Pierce County Sheriff Nancy Hove said the emergency workers were shaken by the scene.

“When it comes to dealing with kids, it’s very tough on everybody,” Hove said.

From the start, officers said weather was not a factor.

For months investigators didn’t know why Milberg drove into traffic, it wasn’t until the snow melted that they found her phone.

After requesting information from Facebook, investigators pinpointed a back-and-forth chat Milberg was having with a man as she drove.

Timestamps show she received her last message at 3:39 p.m. The crash was called in at 3:41 p.m.

In a Wisconsin State Patrol report, it says “Milberg was actively sending and receiving Facebook chat messages just prior to the crash.”

“It is likely,” the report adds, “that driver inattention is a significant contributing factor in this collision.”

The report also says that Milberg’s tires did not have good tread, and that she had a therapeutic amount of oxycodone in her system.

If Milberg is convicted, she faces up to 10 years in prison and/or a $25,000 fine for each of her felony counts.