HOUSTON – It's something you don't see every day: a Houston Police Department horse on the loose in downtown.

WATCH: Horse on the loose in downtown Houston

Police said two citizens were holding a robbery suspect at the JW Marriott.

One of the responding officers was part of the Mounted Patrol and police said that, when the suspect started struggling with the officers, that officer let go of the horse. It got spooked and ran away.

Mark Armes caught part of the incident on camera Tuesday around 10 a.m.

The video appears to have been taken on Chartres Street, near Minute Maid Park.

The horse, named Astro, was in full gallop as it passed Armes.

Houston police said the horse was loose for about five minutes.