The Malabar Hill police have arrested a 24-year-old biker who knocked down a 47-year-old domestic help at the bandstand promenade on Thursday night, causing his death.  Around 9.30 pm on Thursday, Danaram Rawal was cro­s­sing the road near Band­stand police chowkie. Akshay Nasa­re, a resident of Walkeshwar, was heading home on his bike. A constable said, "Nasare was not speeding, but because there was a tree in the way, he did not see Rawal crossing and knocked him down. Rawal fell and hit his head on the ground."