Complex sentence: Lieutenant Daniels' major case unit became aware of Marlo when he met with Stringer, although initially they were unsure if he was working with the Barksdale organization like many other crews in the West side.
Split into simpler sentences: Lieutenant Daniels' major case unit caught on to Marlo when he met with Stringer. Initially they were unsure if he was working with the Barksdale organization like many other crews in the West side.