(CNN) -- The daughter of a West Virginia sheriff gunned down in his patrol car as he ate lunch told CNN on Saturday she believes there is a strong possibility he was targeted because of his crackdown on drug dealing in the area.
Mingo County Sheriff Walter E. "Eugene" Crum had only taken office three months before he was shot to death on Wednesday, but already had built a reputation for targeting drug dealers and so-called "pill mills."
"My dad fought tirelessly against drug abuse. He just wanted to clean up the county and make it a better place to live," Crum's daughter, Julie Hall, told CNN's Fredricka Whitfield in her first television interview since her father was killed.
"Things are still under investigation at this time. We really are unsure," Hall said.
She said her gut tells her "it's a strong possibility" his killing is linked to his law enforcement activities.
Investigators have not publicly identified a possible motive in the case, but they have a suspect.
Tennis Melvin Maynard, 37, is being treated at an area hospital after being shot by one of Crum's deputies, authorities said.
A witness saw the shooting and called 911, giving police a license plate number and description of the car, the Mingo County sheriff's office has said.
According to investigators, Maynard was spotted by deputies and led them on a high-speed chase before crashing his SUV. When he got out of his damaged vehicle, he pulled a gun, they said.
Authorities have questioned Maynard twice, including shortly after he was shot. They will not disclose what he said the first time, and they said he was too medicated to give a lucid statement the second time, Williamson Police Chief Dave Rockel said.
A search of Mingo County court records show no criminal arrests or civil cases involving Maynard. His only citation involves failure to wear a seat belt, according to the records.
Maynard's mother, Olgie, told CNN her son spent time a state hospital for mental health issues in recent years.
"He went crazy," she said, explaining her son hadn't been the same since he was involved in a workplace explosion five or six years ago in Alabama. "He was out in the yard yelling. We called the police, and they took him away."
Since then, she said Tennis had gotten more psychiatric help at another mental health center. At home in Ragland, where he lives with his parents, he mostly stayed in his bedroom and watched television.
"He talks a lot to himself," she said. "... He was never violent."
The Bureau of Alcohol, Tobacco, Firearms and Explosives has traced the gun authorities say was used in the shooting of Crum, according to West Virginia State Police.
But police have refused to release the results of the trace at this time or say whether the gun was purchased by the suspect.
Crum made a name for himself within West Virginia law enforcement circles for his Operation Zero Tolerance, the anti-drug enforcement policy that he put into place shortly after taking office in January.
Crum's wife, Rosie, was appointed Thursday to finish the remainder of her husband's term, with an election set for 2014.
"She was the one who knew him best, and knew what he wanted to accomplish," Hall said.
Hall said she and her brother were concerned for their mother's safety in the wake of the shooting, but believes she is the best person to carry on their father's legacy.
"No one can be 100% sure of what's going to happen," she said.
Visitation was scheduled Saturday between 4 p.m. and 9 p.m. at Mingo Central High School, according to the family. A service for Crum is planned for 1 p.m. ET Sunday at the high school.
CNN's Susan Candiotti, Carol Cratty, Ross Levitt and Greg Botelho contributed to this report.