The victim, Abdul Munaf Sheikh, was the founder and chairman of Al-Sofi Group.
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As he came out of his car outside his home on Gulmohar Road in Juhu after offering namaz, the assailant slit his throat and stabbed him multiple times. Sheikh then tried to rush towards the gate of his house and collapsed, a police official said.
Some locals informed the police who reached the spot and took the victim to the hospital where he was declared dead, he said, adding that the body was sent for postmortem.
The official said CCTV footage of the spot showed one person wearing a cap attacking the builder, but the assailant's face was not clearly seen.
Sheikh, whose company constructed several buildings in Mumbai and was also involved in projects of the Slum Rehabilitation Authority (SRA), always used to go out along with his security cover, but on Monday morning, he went out without the guards, the police said.