Square card with white and yellow text against blue background. Card reads, "Mitzvah4Pittsburgh. Some spread darkness. We spread light. Choose a good deed. Choose a Mitzvah. Add light to the world," followed by four options and a place for respondents to list their name and email address. Some names and email addresses have been redacted for privacy.

Note from a member of The Church at Severn Run in Severn, Maryland. The note is enclosed in an envelope with church letterhead, reading: "The Church at Severn Run: Love Well, Live Jesus, Believe Big!" The note inside reads: "You are loved and we see you! Never give up because you mean more than can you imagine. Signed, A friend." The church's contact information is included on the back of the envelope.

Card from a congregant at the Holy Angels Parish. The front cover contains a stock illustration of seven children holding hands around a table with a large goblet and loaf of braided bread, and seven doves. The illustration is labeled: "We are people of God's peace." The inside reads: "We must stick together in times like these because together we are STRONG and no one can take that away from us. Enzo."

Post-it note with handwritten message in black and red marker. The message reads: "Always in our heart."

Post-it note with handwritten message in blue marker. The message reads: "Blessings of love from Israel."

Square card with white and yellow text against blue background. Card reads, "Mitzvah4Pittsburgh. Some spread darkness. We spread light. Choose a good deed. Choose a Mitzvah. Add light to the world," followed by four options and a place for respondents to list their name and email address. Some names and email addresses have been redacted for privacy.

Handwritten note written in black marker on white paper with the first names of the eleven victims of the October 27 attack. Creasing and staining due to exposure to the elements at the Wilkins memorial.

Square card with white and yellow text against blue background. Card reads, "Mitzvah4Pittsburgh. Some spread darkness. We spread light. Choose a good deed. Choose a Mitzvah. Add light to the world," followed by four options and a place for respondents to list their name and email address. Some names and email addresses have been redacted for privacy.

Post-it note with handwritten message in red marker. The message reads: "Stronger than hate. Never forget the day."

Cut out card from a student at West Allegheny Middle School in Imperial, Pa. The front features a hand-colored illustration of a bird with a leaf in its mouth and floral and geometric motifs. The back contains a handwritten note.

Card from a congregant at the Holy Angels Parish. The front cover contains a stock illustration of a haloed dove flying in front of Noah's ark. Due to water exposure at the memorial site, the message in this card has been partially erased. The remaining text reads: "[?] everybody is ok...praying for those...are hurt and kill. [Na]me: Elio age: 10... [Holy Ang]els" CCD."

Post-it note with handwritten message in blue marker. The message reads: "When there is dark be the one who turns on the light."

Letter from a member of the Point Loma Community Presbyterian Church in San Diego, California. The letter reads: "My prayer and heart are with you all. May God's Grace lift yours in this time of sorrow-." Signed with a heart symbol.

Square card with white and yellow text against blue background. Card reads, "Mitzvah4Pittsburgh. Some spread darkness. We spread light. Choose a good deed. Choose a Mitzvah. Add light to the world," followed by four options and a place for respondents to list their name and email address. Some names and email addresses have been redacted for privacy.

Square card with white and yellow text against blue background. Card reads, "Mitzvah4Pittsburgh. Some spread darkness. We spread light. Choose a good deed. Choose a Mitzvah. Add light to the world," followed by four options and a place for respondents to list their name and email address. Some names and email addresses have been redacted for privacy.

Handmade card illustrated with multi-colored crayons on light purple paper. The front features a child's illustration of an animal, perhaps a horse, with its mouth open wide in the shape of the letter C. The back features a blob outlined in brown crayon and other undecipherable imagery.

Card from a student at West Allegheny Middle School in Imperial, Pa. The front features a hand-colored illustration of a bird holding a leaf in its mouth with geometric and floral motifs. The back contains a handwritten note, as well as the stock signature: "From your friends at West Allegheny Middle School."

Card from a congregant at the Holy Angels Parish. The front cover contains a stock illustration of seven children holding hands around a table with a large goblet and loaf of braided bread, and seven doves. The illustration is labeled: "We are people of God's peace." The inside reads: "Just because life is hard now...does not mean it will be forever challenging. Love in stronger than HATE. You just have to strong. We are praying. -Tree of Life members and all Jewish people. - From: Reena Weber and Holy Angels CCD, 8th grade." Illustrated with two small hearts.

Post-it note with handwritten message in red marker. The message reads: "All of New York City feels your pain."