Police say the incidents happened Saturday afternoon in the men's locker room at the facility located on 1530 Yelm Highway Southeast.
"Right now were not sure who the man is, who the suspect is in the case," said Olympia Police Department Public Information Officer Laura Whol.
A 10-year-old boy reported the troubling situation to the front desk at the YMCA around 4 p.m., and employees called police. After investigators arrived, a mother came forward and said the same thing had just happened to her 9-year-old son inside the locker room.
"It's very frustrating," said Mark West, President and CEO of South Sound YMCA. "The safety and well-being of kids are of utmost importance to us."
A surveillance camera captured video of the man police say is responsible for the crime.
"What we're hoping is that we can identify him so this doesn't happen to anyone else," said West.
As investigators continue to work all leads, they hope someone will recognize the pictures and report the suspect's identity to police.
"It does concern me with all measures that are implemented into the Y that something like this happens," said a Briggs YMCA member who did not want his name released.
YMCA members say this is a good reminder for everyone to keep their eyes out for suspicious behavior that could harm an innocent child.
"The little boy did the right thing, and came out, and reported the situation," said West.
It's not clear if the suspect was a member at the YMCA, or if there are other possible victims.
If you have information on who the suspect could be, call the Olympia Police Department at 360-704-2740.