Prosecutors are coming down harder on a 20-year-old man accused of intentionally striking and killing a teenage girl with his vehicle after a fight involving numerous people last month in a Forest Lake park.

A third-degree murder count was amended Monday to second-degree intentional murder against Dylan R. Simmons in connection with the hit-and-run death of 17-year-old Darisha Bailey Vath of Stacy, Minn., on July 16 in Lakeside Memorial Park.

The Washington County Attorney's Office also added three counts of second-degree assault to go with the murder charge and a count of criminal vehicular homicide.

"We are actively pursuing the most serious charges justified by the facts," Laura Perkins, spokesperson for the County Attorney's Office, said in a statement. "As a result of Forest Lake Police Department's continued investigation of the case, there is new evidence to support more serious and additional charges against Mr. Simmons."

The higher murder charge carries with it a longer maximum sentence upon conviction, 40 years vs. 25 for someone found guilty of third-degree murder.

Simmons remains jailed in lieu of $375,000 bail ahead of a court appearance Thursday. His attorney, Kirk Anderson, said Tuesday that "these are only allegations at this point and this case is in the very early stages of the process. Mr. Simmons is presumed innocent of all charges."

The revised criminal complaint says video from an office building near the park was reviewed by police days after the incident and shows Simmons twice speeding toward a group of six people. His third attempt was when he struck Vath, the video reveals. Two among the six told police that Simmons' vehicle hit them.

Court records show that Simmons' driving history also includes convictions for underage drinking and driving, speeding, no vehicle registration, no vehicle insurance and driving after suspension. He also has an open case for driving in April after his license was revoked. At the time of last month's incident, Simmons held a valid driver's license, a state Department of Public Safety spokesman said.

According to the initial filing of the complaint and a related court document:

People there told police there had been "physical fights involving two groups of individuals," the charges read. "Multiple participants had armed themselves with weapons such as a baseball bat, a crowbar and a folding knife."

Simmons and another person got in a car once the situation calmed down. One of the groups hit Simmons' car with the bat, and he claimed he was hit on the arm with a bat.

Simmons then "intentionally drove in the direction of several people from the opposing side of the conflict" and struck the back end of another vehicle that belonged to his rivals and had brought Vath to the park.

Simmons backed up his car and drove toward multiple people close to the vehicle he hit. He "drove over [Vath] with both the front and rear passenger side tires" of his car before driving away with another person with him, the complaint read. Upon return, Simmons admitted running over Vath and said he knew what he had done.