Youths who threw a brick at a moving bus left a female passenger with shattered glass in her eye, according to witnesses.
The terrifying incident happened on Monday afternoon when the Horsforth-bound bus was travelling along Abbey Road near to Kirkstall Forge Station.
Passengers were frightened out of their skins when a brick came hurtling through a window, with one woman left with glass in her eye.
Witness Karen McDonald was travelling on the bus at the time.
She said: "It was really busy and as we came round up to the Forge train station I just heard this smash. I wondered what it was and saw a window smashed.
"I told the driver and he said 'is anyone hurt?', and I said yes, one lady had glass in her eye.
"He pulled up at the next stop and went to make sure the lady was okay and asked if she wanted an ambulance. She said no at first, but after posting about it on Facebook some said there was an ambulance there so they must have convinced her to get checked out properly.
"I asked a few passengers what happened, those at the front weren't too sure, then I heard a guy say to the driver it was two kids. He gave the driver a description and said they threw a brick at the bus.
"People got off as most of us couldn't do anything but from what I can gather the driver seemed like he was doing a good job and people were helping out and staying behind to give their accounts."
Karen added: "You just don't expect a brick thrown at the window when going home from work. It really made me angry - it's not even shaken me up, just made me really mad. Their parents must be dead proud of them."
West Yorkshire Police confirmed they were called to reports of a stone being thrown at a moving bus causing damage to the window yesterday at 4.30pm. Officers were called to Outwood Avenue on Abbey Road and an offence of criminal damage has been recorded, although no arrests have been made.
A spokeswoman for First Buses said: "We're aware of yesterday's incident and are working closely with the police."