Handwritten note in red ink on white paper glued to black paper tag with gold string. The note reads: "Strong Than Hate. RIP."

Post-it note with handwritten message in black ink. The message reads: "Etz Chaim Hi. It is a tree of life for those who hold fast to it."

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

Post-it note with handwritten message in green and red marker. The message reads: "Love is stronger than hate. Rest in peace. Jaime." The "o" in love and the dot in the "i" in Jaime are written with hearts.

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 contains messages of condolence, love, and wishes for strength. The church's contact information is included on the back of the envelope.

Handwritten card from a student at Goddard Middle School in Littleton, Co. The front and back cover reads: "One of the happiest moments ever is when you find the courage to let go of what you can change." The inside reads: "Dear Tree of Life Congregation, I am so very, very sorry for your loss (losses). I know what it's like to lose someone. I am Camden. I am a student at Goddard Middle School. I am 13. I think that what happened with the shooting was not ok. Just because people have beliefs that are different it doesn't give people the right to do something that.

Letter from a member of the Point Loma Community Presbyterian Church in San Diego, California. The letter reads: "My prayers are with you all at the Tree of Life synagogue. May our God ease your sorrow. Know that He is with you. May God bless you all. Eloise."

Card from a student at West Allegheny Middle School in Imperial, Pa. The front features a hand-colored illustration of the words: "Keep Going" surrounded by stars, arrows, and other floral motifs. The back contains a handwritten note, featuring a quote from the British historian, Richard Evans, as well as the stock signature: "From your friends at West Allegheny Middle School."

Post-it note with handwritten message in blue marker. The message reads: "You are loved. You are stronger than hate. Love and more love."

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

Letter from a member of the Point Loma Community Presbyterian Church in San Diego, California. The letter is dated 11/4/18 and reads: "To our people of God. Our prayers of love and support are with you always. The loss of your friends and family is horrible. Our prayers for healing are with you all. God promises in Malachi 4 that 'Goodness will shine like the rising sun and will bring healing.' Take heart. With love, Liliana [last name redacted]."

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.

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

Handwritten sign written in purple, orange, and red marker. The sign reads, "We will not forget you. Love will triumph."

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.

Folded card with colored pencil word art. Cover reads: "Have a good day". Interior reads: "Dear all, I'm so sorry to hear what happened there. We as a Beth Chai would like to send our heart to be there together. We believe world will be better. [Last name redacted for privacy] family."

Post-it note with handwritten message in red marker. The message reads: "Love Wins. Love and prayers from York, AA. T.B.I."

Black and white photograph showing large group of people in a banquet hall. Label taped onto photograph reads, "1955."

Post-it note with handwritten message in green marker. The message reads: "I miss Bubbie."

Large square card from a student at Fountain Valley School in Colorado Springs, Co. Card reads: "Dear members of Tree of Life synagogue, My name is Shi Dao [last name redacted]. I'm from a city in North-East China. I am sorry this tragedy happened. My deepest condolences. May peace be with you. Nov. 5, 2018. From a Chinese in Colorado."