Sunday marks the fifteenth anniversary of Sept. 11, 2001, the day of tragic terror attacks that killed 2,977 people when commercial airplanes hijacked by terrorists were flown into the World Trade Center, the Pentagon and a field in Pennsylvania.

The attacks forever changed the lives of all Americans, but none more so than the victims and their families. The National September 11 Memorial & Museum in New York City will host a memorial ceremony Sunday to commemorate the day’s tragic events and pay respect to the family members of those who lost their lives.

A live stream of the memorial will be broadcast live on the 9/11 Memorial Museum’s homepage and begin as Flight 11 crashed into the North Tower of the World Trade Center. To watch, click here.

9/11
The Tribute in Light is seen on the 14th anniversary of the 9/11 attacks on the World Trade Center at the National September 11 Memorial and Museum in Lower Manhattan in New York on Sep. 11, 2015. Reuters

The broadcast will feature a private ceremony with family members of victims killed in the 2001 and 1993 attacks at the World Trade Center. To honor those killed, family members will read the names of victims. Six moments of silence will occur during the commemoration: two marking the planes hitting the towers, two marking the collapse of the towers and two marking the attack on the Pentagon and the crash of Flight 93 in Pennsylvania.

Meanwhile, the bell of hope will be rung at St. Paul’s Chapel in New York City in remembrance of those killed 15 years ago. Prayers for peace are also scheduled to be said. St. Paul’s Chapel was nicknamed the "little chapel that stood," for remaining intact following the destruction of the twin towers. The chapel served as a point of sanctuary for relief workers after the 2001 attack.

As part of the National Day of Service and Remembrance, volunteers' events were scheduled to be held across New York City. The New York Blood Center was expected to be accepting donations from 9 a.m. to 4 p.m.

The 9/11 Memorial Museum will open to the public at 3 p.m. following the private ceremony. The annual Tribute in Light illuminates New York City’s skyline with two columns of light depicting where the twin towers stood. The tribute can be seen in the sky south of the Memorial Museum until midnight.

For those who can not make it to New York, the Memorial Museum's website features suggestions on how to honor the legacy of the attacks across the country, including lesson plans. The 9/11 Memorial website also lists a number of times of day for moment of silence to be observed at the site. The site reads:

8:46 a.m.: Hijackers deliberately crash Flight 11 into floors 93 through 99 of the North Tower (1 WTC).
9:03 a.m.: Hijackers deliberately crash United Airlines Flight 175 into floors 77 through 85 of the South Tower (2 WTC).
9:37 a.m.: Hijackers deliberately crash American Airlines Flight 77 into the Pentagon, near Washington, D.C.
9:59 a.m.: The South Tower (2 WTC) collapses.
10:03 a.m.: After learning of the other attacks, passengers on United Airlines Flight 93 launch a counterattack on hijackers aboard their plane to try to seize control of the aircraft. In response, the hijackers crash the plane into an empty field near Shanksville, Pa.
10:28 a.m.: The North Tower (1 WTC) collapses. The 16-acre World Trade Center site is in ruins, with collateral damage affecting all adjacent properties and streets. A rescue and recovery effort begins immediately.
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