A BMW is understood to have been involved in a collision with another car in High Street, Brownhills, before striking the baby’s pram at around 4pm on Easter Sunday, West Midlands Police said. The baby was being pushed along the pavement by family at the time and suffered serious injuries.
Police said he was rushed to hospital but nothing could be done to save him.
A relative suffered a shoulder injury but nobody else was injured.
Police said the driver left the scene but a 34-year-old man was arrested in Bloxwich shortly afterwards.
He has been taken into custody and will be questioned on suspicion of causing death by dangerous driving.
Sergeant Mark Crozier, from the collision investigation unit, said: “A baby has tragically died and we’ll be doing all we can to support his family during this deeply devastating time.
“We’re in the process of speaking to witnesses and establishing the circumstances around this collision.
“I would ask anyone who was in the area, and has information which can assist our inquiries, to come forward.
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“We understand the shock this will have caused but I would ask people not to speculate on what happened.”
Police said they are particularly keen to hear from anyone who was in the area and may have dashcam footage, either before or at the time of the collision.
Anyone with information can contact police via FL-COLLISION-INVEST@west-midlands.pnn.police.uk, via Live Chat or by calling 101.