Investigators with the Greenfield Police Dept. are urging anyone who may have been sexually assaulted by Daniel Acker to contact authorities.  Acker, 61, is a swim coach from Waukesha accused of assaulting boys for nearly four decades. 

Police believe the assaults began in the 1970's.  The victims all ranged in age from 7 to 15 when the crimes were committed.  He may have committed hundreds of assaults on dozens of victims. 

"We want to offer the victims the opportunity for some sort of closure," Greenfield Deputy Inspector Bradley Wentlandt said during a news conference Friday.  "We want to bring Acker to justice."

Police took Acker into custody on charges of sexual assault of a child.  The victim in the case is now 19 years old and from West Allis.  But he claims he and Acker started having sex when he was 15 or 16.  He says the two are still in a sexual relationship today.

The report also mentions four other victims who are much older now.  One man claims he met Acker through a friend of his father.  He later told police that Acker assaulted him at least 100 times.  The man's brother says Acker assaulted him as well.

Two other victims mentioned in the report say Acker assaulted them when they were seven.  One claims an adolescent treatment center assigned Acker to him as a big brother.

"Because of the statute of limitations, none of the cases from the 1970's are prosecutable," Wentlandt explained.  "Right now, our case is the 19-year-old West Allis man because it was a recent assault."

Authorities issued a phone number for victims to call, in order to help build their case. 

"We know it's difficult for people to come forward," Wentlandt said.  The number for victims is 414-761-5301.

During the investigation, police found children's toys and a large model of a police station in his home.

"On the walls of that model, he had photos of children that had been abducted and murdered," Wentlandt said.  "He has a strange infatuation with child murders."

Police say Acker has no prior criminal record so he came up clean on background checks.  Police say he preyed on 'at risk' youth. 

Acker is currently an employee of the West Allis Recreation Department working with the swimming programs.  He's been placed on un-paid leave from that job.

In addition to working in West Allis, Acker has been a swim coach and lifeguard for more than 40 years.  He was also an employee of the Milwaukee County Mental Health Complex and the Child/Adolescent Treatment Center.