A passenger called out a Sheffield bus driver for appearing to use his phone behind the wheel.
Steven Chapman, from Sharrow Vale, said he was travelling home on the 81 bus bound for Dore when he spotted the driver on his mobile in moving traffic.
The 29-year-old took a picture of the driver and posted it on social media.
Mr Chapman said 'felt unsafe' and asked to get off the bus as it made its way up Ecclesall Road in heavy traffic on Tuesday.
Bus bosses have told The Star the incident will be 'fully investigated as a matter of urgency'.
Bus driver Paul Andrew Brown was jailed for 10 months in April 2017 after he knocked over and killed 15-year-old Summer Seymour on Haymarket in Sheffield city centre and seriously injuring boyfriend Jake Ford.
The prosecution said in run up to the horror crash, Brown’s ‘attention was not fully on his driving’ and CCTV images showed him using his phone at the wheel and logged off the ticket machine minutes before the collision.
The analyst said he first noticed something was amiss as the vehicle pulled out of the bus stop at Waitrose on St Mary's Gate.
"The bus pulled out and I spotted out of the corner of my eye the driver wasn't doing what he should've been.
"I saw he was on his phone and I took a picture of it. I said 'you can't be serious, put your phone away' and he did straight away but he was angry I took a photo of him.
"It's a moment of madness on his part. A stupid decision. I cycle around Sheffield a lot and the amount of drivers you see not paying attention as because they're on their phone is ridiculous.
"I'd just say please don't do this again - not just to the bus driver but to anyone who think of using their phone behind the wheel.
"Nothing can be that important for them to use it - so many people are injured or killed because of it."
Andrew Simpson, operations director at First South Yorkshire, said: “We thank our customers for bringing this to our attention, the safety of our customers is our highest priority.
"We do not tolerate any action from any employee that may compromise the safety of our customers. Drivers must remain focused and alert at all times while in control of the vehicle and therefore, we are very concerned to learn of this allegation. This incident will be fully investigated as a matter of urgency.
“Our mobile phones policy is very clear that hand held or hands free mobile devices must not be used whilst driving and compliance with this policy is mandatory.
"We insist that drivers’ mobile phones are switched off or switched to silent, and put out of sight to avoid any distractions. In the event that a call must be made to the operations team then the vehicle should be parked in a safe place with the engine switched off.”