Ruby on Rails Action mailer multiple attachments

I am making a feature to allow user to attach multiple attachments while sending the email. I have added multiple:true and multipart:true but am not been able to attach multiple attachments. Please help me how can I do that. Also, please mention, how can I display the uploaded file names , 1 after another. Note: I am using paperclip

My code:

Form.html.erb

<%= form_tag mass_mail_reseller_path, :multipart => true, class: "new-mail-form form-horizontal" do%>
        <div class="row form-group">

        <div class="row form-group">
          <%= label_tag "attachment", 'Attachment:', class: "col-sm-1 control-label"%>
          <div class="col-sm-10">
            <%= file_field_tag "attachment",  multiple: true %>
          </div>
        </div>
    <% end %>

my_controller.rb#action

def mail_reseller
    _from = params[:from]
    _to = get_resellers_mail_Ids(params[:to])
    _subject = params[:subject]
    _content = params[:body]
    if params[:attachment]
      _filename = params[:attachment].original_filename
      _file = params[:attachment].read
    end
    Resque.enqueue(ResellerWorker, _to, _from,  _subject, _content, _filename, _file)
    flash[:notice] = "Mail has been sent."
    redirect_to reseller_admin_path(:project_id => 'lead_tracking_reseller')
    # directory = "#{Rails.root}/files"
    # path = File.join(directory, _filename)
    # File.open(path, "wb") { |f| f.write(params[:attachment].read) }
  end

mailers/my_mailer.rb

def mass_mail_resellers _to, _from, _subject, _content, _filename, _file
    attachments[_filename] = _file if (_filename && _file)
    @mail_body = _content
    mail from: _from,
         to: _to,
         bcc: 'jam@company.com',
         subject: _subject
  end