Police are looking for a 25-year-old man who was last seen walking toward South Mountain near 35th Avenue and Dobbins Road on May 15.
Brian Histand hasn't been seen since his friends saw him near South Mountain over a week ago. They believe he may have been confused two days prior to disappearing due to a possible concussion while BMX riding or it could have been a result of post-concussion syndrome.
Brian's father, who is a police officer in Pennsylvania, isn't giving up hope.
"We are on the move from very early in the morning until late in the evening, so it keeps us busy and keeps us actively involved to find Brian," said Michael Histand.
The morning before Brian vanished, a police officer spotted him in a field -- naked. The officer let him go after determining he was coherent. Later, Brian's car and BMX bike were found near South Mountain, but there was no trace of him.
"He hasn't used his helmet many times and taking pretty good head shots over the years unfortunately.. we think that might be playing a role in this," said Michael.
Detectives are telling Michael that someone may have spotted his son just a week ago.
"He was sitting in the middle of the field with his legs crossed that seems to be consistent with the prior behaviors that had been observed two weeks ago."
But tip after tip -- and no solid leads pointing to his son's whereabouts.
"It will be difficult to make the decision when to go home, but we are not there yet," said Michael.
Brian's vehicle, wallet, ID, credit cards and bicycle were found on May 17 after his keys were seen in an open field.
He's described as white, 5'9", about 140 pounds with blue eyes and brown hair.
According to friends, he's known to enjoy hiking trails in South Mountain Park.
If you have any information about Brian's whereabouts, call the Phoenix police.
TIP LINE: 602-534-2121
Friends and family set up a page for him at: www.facebook.com/BrianHistandMissingPerson