Friends and family will remember the father and son who died in a plane crash Sunday night.

The Wenig Funeral Home's website says the visitation for 45-year-old David Holtrop and 16-year-old Max Holtrop will be held on Friday at Bethany Reformed Church in Sheboygan from 1 p.m. to 7 p.m. and Saturday from 9 a.m. to 10:30 a.m. Funeral services will follow the visitation on Saturday.

David and Max Holtrop were on their way home from a paintball convention in Minnesota when their plane went down southeast of Osseo. There's still no word on what caused the single engine plane to crash. The National Transportation Safety Board expects to have a preliminary report on what happened out by the end of the week. It could be a year before we have a final crash report.
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STORY FROM 6/8/09
We now know more about the victims of Sunday night's fatal plane crash in Jackson County and their ties to the Chippewa Valley.

Colleagues say 45-year-old Dr. David Holtrop and his 16-year-old son Maxwell were on their way home to Sheboygan from a paintball convention in Minnesota. Dr. Holtrop is a chiropractor in the town about an hour north of Milwaukee.

According to Dr. Holtrop's on-line biography, he practiced in Chippewa Falls for a year and a half before moving to Sheboygan in 1989.

His co-workers say Sunday night's crash was a tragic end to a father-son weekend getaway.

"I got a phone call this morning at 1:30 a.m. It was the biggest surprise of my life," says Dr. Russ Petersen.

Petersen says when Holtrop's plane went down, he lost a good friend and a great medical partner.

"Dr. Holtrop had an amazing way of impacting people's health naturally. He loved this clinic. He loved seeing people's lives change," Petersen says.

Another colleague says Dr. Holtrop died doing two other things he loved—flying and spending time with his family. Holtrop and his 16-year-old son Max were on their way home from a paintball convention in Minnesota. It was a 16th birthday present to his son.

Max was "very creative, very artistic. He was just working on an animation short that he was going to present this week," says Ted Hamm, the administrator at Etude Arts Charter School where Max Holtrop spent his afternoons. "The students were so devastated by the loss. It was just a lot to take in."

Hamm says Max was a talented young artist. He was the oldest of the Holtrop's four children. Dr. Peterson says David was a man of great faith.

"He honored God above all else,” Petersen says.

Sunday night, emergency responders used ATVs to search for the downed plane. Several people called the sheriff's department about 6 p.m. after hearing a plane sputter and crash. (Click here to hear from one man who called 911)

The crash site is only accessible by small trails and ATV’s and those trails are in bad shape with all the rain. It’s slowing down investigators who are trying to find out why the plane went down.

"It's definitely hilly terrain and back roads are all gravel,” says Jackson County Sheriff Duane Waldera.

David Holtrop and his son Maxwell were flying back from Minnesota last night. Now, pieces of the single engine Grumman American plane are scattered through the trees on this hillside.

"Just getting back to the location has been somewhat difficult and we were fortunate where the wreckage was located it's off a small path made by a property owner,” says Waldera.

Someone who lives in the area found the wreckage last night. Then investigators used ATVs to reach the crash.

"They processed the scene the best they did last night, and they did find two bodies,” says Waldera.

The Federal Aviation Administration and the National Transportation Safety Board arrived this morning to take over the investigation.

"They plan to get most of the wreckage removed today,” says Waldera. “A lot of information hasn't been confirmed. We're waiting on the flight plans and there's pretty good records they have to maintain."

And while the continuing rain showers make investigating difficult, Waldera says the weather may have been a factor in why the plane went down.

"It's a bad weekend for air travel, I would think. We couldn't get any aircrafts up either for anything, so it was a difficult weekend.,” says Waldera.

Waldera says there is a small landing strip a few miles north of where the crash happened, but it hasn't been determined whether the plane was planning to land there.

NTSB Investigator Andrew Todd Fox says he expects to have a preliminary report on what happened out by the end of the week, but the full cause of the crash may not be determined for nearly a year.

Chief Deputy Mark Moan says around 6 p.m., a man called the sheriff's department after hearing the plane sputtering. The man then heard an explosion and then didn't hear the plane after that. Then two more people called 911 and reported the same thing.

During the search, the Federal Aviation Administration (FAA) checked with local air traffic control towers but no one reported a missing plane.