"A police officer called out to me as I was riding by on my bike."
"A police officer" 「警察」"policeman" 「男」" "policewoman" 「女」, "cop" も使えます。
"called out " 「声をかけた」
"a police officer called out to me" 「警察に声をかけられた」
"as I was riding by on my bike" 「バイクで走っている時に」
"as~" 「時」
"riding my bike" 「バイクで走っている」
"riding by on my bike" 「バイクで通り過ぎた」