The incident happened around 3:30pm on Bellaire Boulevard just west of Cook Road.
The Houston Police Department says two teenage girls were crossing Bellaire from a tree-lined median when one of them was struck by a METRO bus heading westbound on the road.
It's not clear how fast that bus was traveling, but it was fast enough to leave behind evidence of the impact: a cracked windshield and damage to the front panel near the bus' headlight.
We spoke with the mother of the friend who made it across the street. That eyewitness told her mom the girl was thrown several feet by the force of the impact.
"It was her friend, and they were on their way to the store. They were trying to catch the bus and all I know is that she called me screaming and hollering and I came right away," said Shevaughna Lockley, mother of the eyewitness.
We actually started talking to that bus driver and as he started explaining to us what happened, a representative from METRO pulled him away so we don't yet know his side of the story.
The mother of that eyewitness says the teen suffered both arm and leg injuries and some scrapes to her face. METRO Spokesperson Jerome Gray says the teen is in critical condition at Memorial Hermann Hospital.
We're told the victim is a 15-year-old student at nearby Hastings High School.
Gray says there was no crosswalk where the teen was walking but the driver will undergo the standard drug and alcohol tests. Per METRO policy, Gray says the driver also will be pulled off the streets until an initial investigation is complete.
Several people were aboard the bus when the wreck happened.
Police have shut down two lanes of Bellaire Boulevard as they continue to investigate.
Stay with Eyewitness News and abc13.com for the latest details.