It happened along Sims Bayou near Broadway, and Eyewitness News spoke with the family that witnessed it and confronted the man.
"He knew what he was doing. If he didn't know what he was doing, he would not have run when he got caught," a woman said. "I was angry, disgusted."
The witness fears retaliation and asks to be identified only by her last name, Jones.
On Sunday morning around 9 a.m., Jones and her family were out on a bike ride when a woman ran up to them in tears.
They said that the woman told them about a man she said was touching himself on the trail.
The family confronted the man, screaming at him until he ran away.
Now, they worry he will do it again.
"I saw the terror in that old lady's face, and it kind of just set in what he was doing out here, and it hurt my feelings," Jones' son, Stephen Rawlinson, said.
They say he was wearing a full face covering and sunglasses, so they don't have a clear description of him.
Deputies say they are increasing patrols along Sims Bayou.
"If I've got to take him down again and prevent him from doing this to other people, I will," Jones said.
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