ANNAPOLIS, MD — Lawmakers and the parents of a slain Columbia high school teacher have teamed up to try to increase penalties for killing pregnant women. The current Maryland law interprets the act of killing a fetus as homicide only if the unborn child is old enough to exist viably outside the womb.

Laura Wallen, 31, was four months pregnant when she disappeared before the first day of school in Howard County. Wallen was a beloved teacher at Wilde Lake High School in Columbia. Police found Wallen's body buried in a field in Damascus on Sept. 13.

Her boyfriend, Tyler Tessier, 33, was charged the next day, and is scheduled to stand trial on a first-degree murder charge on April 9, 2018.

The autopsy report showed Wallen, who was 14 weeks pregnant, was shot in the back of the head, authorities said.

"A monster with one bullet killed two generations of our family," the victim's father, Mark Wallen, said at a press conference on Tuesday, Jan. 30, in Annapolis, where he and his wife were advocating for a law to protect unborn children, regardless of the stage of pregnancy, if he mother is murdered. Because the unborn child was not viable outside of the womb, Montgomery County State's Attorney John McCarthy told NBC that Tessier was indicted on one murder count rather than two in Wallen's death.

Homicide is the leading cause of death among pregnant women, according to a study from the Maryland Department of Health, which found it usually occurs in the first three months of pregnancy, with firearms the most common method.

"There is research that shows it is the pregnancy that puts the woman at risk, and her pregnancy put her at risk," Gwen Wallen said of her daughter at the press conference, which was broadcast by WBAL Radio.