Police chiefs from around the country are gathering in Philadelphia for an annual meeting expected to draw thousands of participants, including U.S. Attorney General Eric Holder.
The International Association of Chiefs of Police meets through Tuesday.
Holder is scheduled to speak on Monday, along with FBI Director James Comey.
A day later, Boston Police Chief Edward Davis is set to discuss the Boston Marathon bombing.
The conference will also feature a session on the Sandy Hill school shooting in Connecticut, along with panels on officer-involved shootings and cyber attacks, Philadelphia Police Chief Charles Ramsey opens the event with remarks Saturday.
The gathering is being held at the Pennsylvania Convention Center.