RIVERVIEW, Mich. -- A Riverview man is going public with recognition for those who helped put away the man he said is responsible for his son's death.

Bill Towle has a sign in his front yard stating what happened in the summer of 2006 that took his son's life. He congratulated the Wayne County Sheriff's department and the prosecutor's office for their role in putting the man that sold drugs to his son in jail.

Towle's son, Billy, 28, was a heroin addict. In the summer of 2006, Towle, Jr., bought some drugs laced with fentanyl. Investigators said the combination killed him and hundreds of others over the same summer.

"He never hurt anybody but himself," Towle said.

Towle said he spent months investigating his son's death and said he felt the Riverview police did nothing because they were treating his son's death as an overdose.

"I made a promise at his coffin that I would get this guy no matter what it takes," Towle said as he choked back tears

He called the Wayne County Sheriff's department, and a detective with the Drug Enforcement Agency began investigating and arrested Gregory Finley.

"I go to his gravesite every day. Your kids are supposed to bury you. You're not supposed to bury them," Towle said.

Riverview police said they handled the case properly.

"My officers did nothing wrong. Mr. Towle has his feelings. They are wrong in my opinion," said Chief Don Ginestet. "My officers did a fine job investigating the case. They turned over all of their evidence to the county."

Finley was sentenced on Tuesday to 20-30 years. He was the first person to be charged in Michigan under the homicide statute for selling the drugs that killed Towle.

"All they really allowed to happen was for the guy to conduct his business for another five months. So, he exposed alot of other people to potential harm," Towle said after the sentencing.