Mumbai: Govt Railway Police (GRP) investigating the incident of a disabled commuter being pushed off a moving local train and killed have found a crucial eyewitness who is speech and hearing impaired. An expert assisted investigators on Friday to interpret the witness’s account.Cajetan Pires, a 63-year-old amputee, was travelling in the Divyangjan coach of a Borivali bound local when an argument broke out between him and a co-passenger, Amjad Shaikh, over seats on Thursday. The witness told the police that he was in the same compartment when Pires boarded at Mahim station. Shaikh had started his journey from Lower Parel and was occupying a seat. Pires asked him to vacate the seat as he did not have a disability. Shaikh refused to do so and the two men had an argument. The witness recounted other passengers intervening and offering to give up a seat, but to no avail. Eventually, Shaikh got up and grabbed Pires by the shirt collar. As he gave Pires a push, the latter lost his balance and fell out of the train. The GRP also got the witness to write down his account. There were no surveillance cameras in the compartment.“We are building a strong case against Shaikh,” said a senior police officer, adding that Shaikh was travelling without a ticket on the day of the incident.Pires’ funeral was conducted at Santacruz on Saturday. Pires’ family had told TOI earlier that they wanted the strongest possible punishment for Shaikh.