Sohel was gunned down by a still unidentified gang in front of Club Tramps on Kamal Ataturk Avenue at Banani in the city in the early hours on December 18.
Bunty Islam, however, remained at the clinic - Cardi-Hope Heart Centre - under DB custody till the filing of this report last night.
An official of DB seeking anonymity, told The Daily Star last night "We can't hamper his treatment as, according to doctors at the clinic, Bunty has been suffering from some sort of cardiac disease." He, however, could not say when Bunty would be released from the clinic.
With the arrest of Bunty Islam four persons were held so far in connection with the killing of Sohel.
Bunty is an accused also in another case lodged by the Department of Narcotics Control for alleged illegal sale of liquor at his club.