Not including guns when talking about mass killings is "like not including cigarettes when discussing lung cancer," Sen. Charles E. Schumer (D-N.Y.) said as he began a round of questions.

Schumer is expected to emerge as the lead sponsor of legislation that would mandate background checks on most, if not all, gun buyers. He's been speaking with moderate senators, including Joe Manchin III (D-W. Va.), Mark Kirk (R-Ill.) and Tom Coburn (R-Okla.), about co-sponsoring the bill.